dcf.cymru stimulus sheet · Science · Year 10
Raw results: marble chips and hydrochloric acid
These are the results your class collected last lesson. They have not been processed. Nothing has been averaged, rounded or graphed.
What was done
- Question investigated: how does the concentration of hydrochloric acid affect the rate of reaction with marble chips (calcium carbonate)?
- Apparatus: conical flask, bung and delivery tube, 100 cm³ gas syringe, stop clock, balance, measuring cylinder.
- Each run: 5.0 g of small marble chips (2–3 mm) added to 50 cm³ of acid. The stop clock was started when the bung went in and stopped when the syringe reached 20 cm³ of gas.
- Kept the same: mass and size of chips, volume of acid, room temperature (21 °C), same gas syringe.
- Each concentration was repeated three times by a different group.
Table 1: time taken to collect 20 cm³ of carbon dioxide (seconds)
| Concentration of acid (mol/dm³) |
Repeat 1 (s) |
Repeat 2 (s) |
Repeat 3 (s) |
| 0.5 | 96 | 99 | 94 |
|---|
| 1.0 | 51 | 48 | 50 |
|---|
| 1.5 | 34 | 33 | 35 |
|---|
| 2.0 | 25 | 26 | 71 |
|---|
| 2.5 | 20 | 21 | 19 |
|---|
Notes written in the lab book
- "2.0 mol/dm³, third repeat — the bung was not pushed in properly and we could hear gas escaping for about the first 30 seconds. We ran out of time to redo it."
- "The flask felt slightly warm at the end of the 2.5 mol/dm³ runs."
- "The balance reads to 0.1 g. The gas syringe is marked every 1 cm³. The stop clock reads to 0.01 s but we could only react to about half a second."
Safety information from the technician
- Hydrochloric acid at 2.0 mol/dm³ and above is an irritant. Eye protection worn throughout.
- Marble chips are not hazardous. Spills rinsed with plenty of water.